Method of making tubing



P J. w. OFFUTT METHOD OF MAKING TUBING Filed April 23, 1938 PatentedSept. 24, 1940 7 ME'1HOD OF MAKING TUBING John W. Offutt, Ellwood City,Pa,

assignor to National Tube Company, a corporation of New JerseyApplication April 23, 1938, Serial No. 203,945

3 Claims.

This invention relates to a method of making tubing, and particularly toan improved method of making smalldiameter tubing.

Heretofore, small diameter tubes, such as those of from one-eighth toone inch pipe sizes, when not made by the butt-weld process, have beensired diameter.

1 the pieces if they were As is well known, a sinking mill is acontinuous universal mill having grooved rolls, with the grooves in eachsuccessive stand of rolls smaller than those in the preceding stand. Thegrooves in the first stand are slightly less in diameter than the reeledtube and the grooves in the last stand are of the diameter of thecompleted tube. The roll stands, of which from eight to twentyfour maybe used, are arranged in tandem and are usually spaced as closelytogether as their construction will permit. The spacing will vary fromtwelve inches to as much as five feet, center to center.

The tube, while being passed through the sinking mill, does not have asupporting mandrel on its interior so that the reduction-in its diameteris'accompanied by thickening of the tube wall. In order to overcome thiswall thickenin speed increments between rolls are increased to set up astretching efiect between each set of rolls, thereby eliminating thewall thickening eflect as the wall thickness of the tube is actuallyreduced at the same time the diameter is reduced.

However, when the tubes are reduced in diameter in a sinking mill withthe roll speeds adjusted for stretching, the tubes become materiallyheavier in wall thickness on their ends than in ,the middle. Thisthickening, which is of marked degree, extends for a distance from eachend about equal to twice the distance between the roll' stands. This isbecause no pull can be exerted on a given section of its length unlessthe tube is pped simultaneously between two or more pairs of rolls, acondition that does not exist when the tube is entering or leaving theroll train forming the sinking mill.

That is to say, there can be no stretching until after the front end ofthe tube has'entered the second stand of the rolls and there will benone after the rear end stand.

As the thickened ends of the reduced tubes or pipe are constantregardless of the length of the finished piece, obviously-it would notbenecessary to cut oil and scrap as great a percentage of long as ifthey were short and it is among the objects of We present inven' emergesfrom next to the last erably a nun welder 2 suitably tion to provide formanufacturing purposes as above described long lengths of tubing inplace of short ones.

It is one of the objects of this invention to provide a method ofmanufacturing small diameter seamless tubing wherein the scrap isreduced to a minimum.

It is another object of the invention to provide an improved method ofmanufacturing tubing wherein tubing of a lighter gauge can be made thanby any method heretofore known.

It is a further object of the present invention to provide an improvedmethod of joining the ends of several lengths of tubing together as anaid in the manufacture thereof.

Various other objects and advantages of my invention will more fullyappear during the course of the following specification, and will beparticularly pointed out in the appended claims.

In the accompanying drawing, I have shown for the purpose ofillustration one embodiment which myinvention may assume in practice.

In this drawing:

Figure 1 shows a plan of several pieces of apparatus used in connectionwith my improved method;

Figure 2 is a view showing three lengths of pipe welded together;

Figure 3 is an enlarged plan, partly in section, showing two ends beingwelded together;

Figure 4 is an enlarged plan, partly in section, showing the weld beingcompressed; and

Figure 5 is a view showing the pipes after being reduced in size withthe weld and short crop removed.

In the manufacture of seamless tubing, after the lengths of tubing havebeen formed by piercing round billets or by casting, or in any-otherknown approved manner and suitably rolled, they are ready to be sized.In order to'produce a small diameter tubing, usually less than threeinches in diameter, the tubing is passed through -a sinking and sizingmachine, as has been described.

It will be understood that the maximum length at which rolled tubes canbe commercially produced is limited (usually not over forty feet) and,in order'to produce tubes of greater lengths, it would be n to joinseveral short tube lengths together.

According to the present invention, the adiacent ends of several lengthsof tubing are joined together by welding after the rolling and reelingoperations and prior to the sinking and sizing operation, as heretoforedescribed.

Referring to the drawing, there is shown pref-, positioned on theentering side of a furnace 3. The furnace is adapted to reheat thetubing uniformly to a temperature approximately just below thescaleforming point as it passes therethrough. From the furnace thetubing passes directly into the first stand of the sinking rolls I andthrough the mill where it is elongated and reduced in size to thedesired diameter.

A traveling flash welder is shown and preferably used for welding theends of'the tubes together, but it will be understood that any suitableand practical welding device may be employed that will weld rapidly soas to keep up with the speed of the rolling mill.

In order to maintain as efficient and strong a weld as possible, it isdesirable to allow both the outside and inside flash or overfill 4 and5, re-

respectively, to remain on the tubing, as shown in Figure 3. The insideflash 5 does not interfere with the sinking and sizing operations butthe outside flash 4 would tend to interfere with the tubing passingthrough the roll grooves. In order to eliminate this condition withoutgrinding or shearing, it is proposed to reduce this outside flashdiameter to at least the outside diameter of the tubing, preferably bycompressing the flash inwardly (as is shown in Figure 4) in a suitabledie or roll 6 positioned between the welder and the sinking and sizingmill or reheating furnace.

If it is not practical to weld the ends of the tubes together in atraveling flash welder, due to the speed with which the tubes are fedthrough the reducing or sinking mill, it is proposed to weld about threelengths of tubing about .thirty feet long together to make about aninety foot length. A tube of such length could then be passed into atunnel reheating furnace as it is welded and after the secondand lastweld passed directly into the sinking and sizing mill located at theopposite end of the furnace.

With this arrangement the tube would not be in the welder and reducingmill at the same time, and could be stopped to make the welds in astationary welder. The crops or scrap to dispose of the thickened endswould then be only onethird that necessary from a thirty foot lengthtube. For example, if the ninety foot tube is elongated to three timesits original length in a stretching the total length will be two hundredseventy feet. Ii the roll centers were spaced twelve inches apart, whichis entirely practical, and the thickened ends were two and one-hair"times the roll spacing or two and onehalf feet long, the total crop orscrap loss due to end thickening would be five feet; or less than twoper cent. of the total tube length, which is a very reasonable figure inany tube making process.

As the tubes made by my improved method will be from fifty to onehundred or more feet in length instead of a mam'mum of from thirty toforty feet, and as the length necessary to cut ed the ends of the tubesto remove the thickened portions is comparatively short, say not overfive percent, I am enabled to make seamless tubes of small diameter andthin wall with a scrap loss so small as to make the method practicableon a commercial scale. While I have shown and described an embodiment ofmy invention, it will be understood that this embodiment is merely forthe purpose of illustration and description and that various other formsmay be devised within the scope of my invention, as defined in theappended claims.

I claim:

1. In the manufacture or metal tubing of predetermined lengths, themethod comprising the steps of continuously supplying lengths of tubularblanks of a predetermined size, successively welding the adjacent end ofeach of said lengths to the end of the foremost length so as to form acontinuous length of tubing, successively compressing the flash of eachof the welds between each of the successive joined lengths by forcingthe welds together with the ends of the tubular blanks which theyrespectively join inwardly so that the outer diameter of the weldedjoints is no.greater than that of the tubular blanks, passing thecontinuous length of tubing into and through a reducing mill so as toelongate the same and reduce it to the desired predetermined diameterand size, and finally removing each of the welded joint portions thereintogether with the inwardly bent ends of the tubular blanks and scrappingthe same so as to provide a plurality of lengths of tubing of apredetermined length having a uniform wall thickness throughout.

2. In the manufacture of metal tubing of predetermined lengths, themethod comprising the steps of continuously supplying lengths of tubularblanks of a predetermined size, successiely welding the adjacent ends ofeach of said lengths to the end of the foremost length, successivelycompressing the flash of each of the welds" between each of thesuccessive lengths by forcing the welds together with the ends of thetubular blanks which they respectively join inwardly so that the outerdiameter of each of the welded joints is no greater than that of thetubular blanks, continuously and successively heating the joined lengthsof tubular blanks to a predetermined temperature, passing the joinedtubular blanks continuously into and through a reducing mill so as toelongate the same and reduce the blanks to a desired predetermineddiameter and size, and finally removing each of the welded jointportions therebetween together with the inwardly bent ends of thetubular blanks and scrapping the same so as to provide a plurality ofpredetermined lengths of tubing having a uniform wall thicknessthroughout.

3. In the manufacture of metal tubing, the

'method comprising the steps of continuously supplying lengths oftubular blanks, rolling and reeling each of said blanks, successivelywelding the adjacent ends of each of said lengths to the end of theforemost length so as to provide a continuous length tubing,successively compressing the flash of each of the welds between each ofthe successive lengths by forcing the welds together with the ends ofthe tubular blanks which they respectively join inwardly so that theouter diameter of each of the welded joints is no greater than that ofthe tubular blanks, continuously passing the continuous length oftubinginto and through a furnace so as to heat the same to apredetermined temperature as it passes therethrough, then continuouslypassing the same into and through a reducing mill so as'to elongate thetubing and reduce it to the desired predetermined diameter, and finallycutting the continuous length tubing at each of the welded jointportions therein so as to remove the welds together with the bent endsof the tubular blanks and scrapp g the same so as to provide a pluralityof lengths of tubing of a predetermined length having a uniform wallthickness throughout.

59ml W. OFFUTT.

